Synthesis and properties of LiMn2O4 from hydrazine hydrate reduced electrolytic manganese dioxide

Using N2H4·H2O as reductant γ-Mn3O4 particles were obtained from the electrolytic manganese dioxide (EMD). Via high temperature solid-phase reactions, spinel lithium manganese oxide (LiMn2O4) was produced using the obtained γ-Mn3O4 as precursor mixed with LiOH⋅H2O for the lithium ion battery cathodes. Atomic absorption (AAS) shows that after the liquid-phase reduction reaction the impurity ions, such as Na+, K+, Ca2 +, and Mg2 +, are greatly reduced. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that γ-Mn3O4 has high crystallinity and uniform size-distribution. Spinel lithium manganese (LiMn2O4) synthesized by the γ-Mn3O4 precursor has a high crystallinity and the (111) face grows perfectly with a regular and micron-sized octagonal crystal. The electrochemical tests show that LiMn2O4 synthesized by the γ-Mn3O4 precursor has greater discharge capacity, better cycle performance, and better high-rate capability compared with LiMn2O4 synthesized by the EMD precursor. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicate that LiMn2O4 synthesized by the γ-Mn3O4 precursor has a better electrochemical reaction reversibility, greater peak current, higher lithium-ion diffusion coefficient, and lower electrochemical impedance. Furthermore, this synthesis process is simple, of low-cost, and easy for a large-scale production.

► γ-Mn3O4 can be obtained from EMD reduced by hydrazine hydrate.
► The impurity ions of γ-Mn3O4 can mostly be reduced after the reduction reaction.
► The electrochemical properties of LiMn2O4 synthesized by γ-Mn3O4are better.